1. Field of the Invention
The present invention relates to a vehicle seat including a seat cushion configured to support a weight of a sitting passenger from below and a seat back configured to support an upper body of the sitting passenger from a back side thereof.
2. Description of the Related Art
When turning a vehicle, a driver operates a steering wheel to the left or right side. Therefore, an upper body of the driver is inclined inwardly in a turning direction of the vehicle according to the steering wheel operation. FIG. 6 shows a movement of an upper body of a driver as seen from a back side of the driver when the driver of a vehicle operates a steering wheel to the left side so as to turn the vehicle leftwards. Here, a shoulder line PS of the driver is lowered at the left from a position shown with a broken line to a position shown with a solid line, and a waist line PL is raised at the left from a position shown with the broken line to a position shown with the solid line, so that the upper body is bent. That is, as the steering wheel is operated leftwards, the upper body (shown with a triangle in FIG. 6) of the driver is inclined leftwards about the waist part, so that it forms a tilted L shape, when seen from the back side. In FIG. 6, a reference numeral PH indicates a position of a head of the driver. Also, it has been empirically known that a passenger other than the driver also tilts the upper body in the turning direction of the vehicle against a centrifugal force resulting from the turning of the vehicle. At this time, since both the driver and the other passenger lean the upper bodies against the seat backs, they raise the upper bodies from the leaning state against the seat backs to reduce friction between the upper bodies and the seat backs or tilt the upper bodies against a frictional force such that the upper bodies are separated from the seat backs so as to tilt the upper bodies, as described above. Accordingly, the passenger cannot smoothly tilt the upper body in a left-right direction.
Although a technical object is different from that explained above, there has been developed a technique in which a seat back and a seat cushion are rotated in a vehicle roll direction with respect to a traveling direction of a vehicle so as to cope with the centrifugal force occurring at the turning of the vehicle such that a posture of a passenger is stable at the turning (refer to JP-A-S57-126734).
The seat of JP-A-S57-126734 is applied with a counter measure against the problem occurring at the turning of the vehicle. However, it is not possible to solve the technical object that the passenger can smoothly tilt the upper body in the left-right direction at the turning of the vehicle. That is, according to JP-A-S57-126734, the seat is rotated by the centrifugal force at the turning of the vehicle. However, since the upper body is tilted in the left-right direction at the turning of the vehicle before the centrifugal force is applied, the configuration of rotating the seat by the applied centrifugal force cannot solve the technical object that the passenger can smoothly tilt the upper body in the left-right direction at the turning of the vehicle.